C1: Just power to L29, the breakpoint against Mewtwo for 13 attack IV. It's better to find a Ttar raid, and pinap the Ttar.
C2: No. Evolve one of the karps.
C3: No. Find high level Exeggcutes on a sunny/windy day. Or Bulbasaurs on a sunny/cloudy day
C4. Hold it first.
C5: No. Just walk more Eevees for Espeon. I caught 5x 790+ Eevees in 2 hours on a partly cloudy day. And don't use the fast TM on Alakazam!
C6: No. That's a big investment just for one purpose. Even powering the Alakazam is better than this imo, especially now with battle parties.
C7: No. L20 Steelix sucks on defence, it's about on par with a L30 Cloyster. L20 Chansey does well on defence though.
C8: Up to you.
Fast TM your Blissey.
You don't actually need to power up anything extra for Groudon. Here in SG, you can just go to any raid before the egg hatches, get into the first lobby, just use 1 Eggy/Gary each and finish the raid.
You should definitely be able to solo Close Combat Machamp with 2 Espeons, 2 Eggys and 2 Dnites. Order:
Espeon C/FS
Espeon C/Pb
Eggy C/Psy
Eggy C/SoB
Dnite DT/Hu
Dnite DT/O